Book excerpt: According to a recent FBI study of serial murder, it has climbed to an `almost epidemic proportion'. It is believed that there are currently up to 6000 people a year dying at the hands of serial killers. The FBI and other law enforcement agencies estimate that there are between 35 and 50 serial killers on the loose at any given time. Other estimates put the number of killers closer to 500. In either case, officials expect these numbers to continue their dramtic rise. This is an up-to-date edition of an original in-depth study of serial killers at large, written by one of the world's foremost authorities.